Abstract: Aiming at problems existed in saturation evaluation of regulative wells in high water cut stage, the authors studied the relationship between resistivity (I) and water saturation (S_w) in waterdriveoil process through rock physics experiment for simulation of the oilfield development. It is a contradiction to the oildrivewater approach, relation between resistivity and water saturation in duallogarithm coordinates system in waterdriveoil process appears a nonlinear pattern, which shows an obvious two sections that corresponds respectively to high and low zones of water saturation. Saturation (S^wp) related to the twosection inflexion varies as wetness alters, therefore the final oil recovery also varies in waterdrive approach. Characteristics of I-S_w curve under waterdriveoil process show that resistivity curve can not reflect the water saturation exactly in high water cut stage of oilfield development. Thus it is unsuitable to evaluate water saturation in middle and later development stages using model derived from oilwaterdrive experiment in exploration stage and early development stage. It is especially inappropriate in the high watercut stage, in which resistivity represents poorly water saturation so that the evaluation accuracy is severely limited.

Key words: oildrivewater (drainage), waterdriveoil (imbibition), resistivity index, water saturation, high water cut stage, wetness, final oil recovery